Structural and magnetic characterization of weberite-type RE3NbO7 (RE = Gd, Dy, Ho, and Er) ceramics with notable cryogenic magnetocaloric responses
The magnetocaloric (MC) responses of rare-earth (RE)-dominated magnetic solids have been extensively investigated to develop high-performing MC materials for cryogenic cooling. Herein, single-phase RE3NbO7 (RE = Gd, Dy, Ho, and Er) ceramics were fabricated via solid-state reactions, and their structural and magnetic properties, specifically cryogenic MC responses, were determined through experiments and theoretical calculations. All RE3NbO7 ceramics crystallize in the orthorhombic weberite-type structure (space group C2221, No. 20). The constituent elements are uniformly distributed, with RE3+, Nb5+, and O2− valence states. All ceramics exhibit considerable cryogenic MC responses, identified by maximum magnetic entropy change (−ΔSMmax), temperature-averaged magnetic entropy change (−ΔSMavg), and relative cooling power (RCP). Under ΔH = 0–7 T, the MC parameters are: Gd3NbO7: 33.76/30.57 J/(kg K) and 362.23 J/kg; Dy3NbO7: 19.39/18.72 J/(kg K) and 444.39 J/kg; Ho3NbO7: 18.52/18.20 J/(kg K) and 495.9 J/kg; Er3NbO7: 20.26/19.31 J/(kg K) and 345.45 J/kg. These values are superior to those of RE3RuO7 ceramics and comparable to recently reported RE-dominated MC materials, indicating promising potential for cooling applications.